Thomas Pearsall - Academia.edu (original) (raw)
Papers by Thomas Pearsall
Performance with the spark-ignition conversion, exceeded that with diesel pilot fuel. Effect of v... more Performance with the spark-ignition conversion, exceeded that with diesel pilot fuel. Effect of varying the compression ratio was also investigated. Direct injection. of liquid ammonia into a high compression ratio (30: 1) engine was attempted and was unsuccessful. Various other auxiliary aids such as fuel at ditives, ionization and radio frequency dissociation were also investigated. A total of 1128 engine test hours were accumulated on the sparkignition engine of which 1045 were with ammonia fuei; 954 hours (911 with ammonia) were accumul'ated onthe compressi t-ignition engine. FOREWORD Logistics studies of Army operations, in World War II and Korea established, that apprcximately 65 percerft of the tbtal tonnage required for support of combat-operations iconsisted of fuels and lubricants. To compound this already heavy logistical, burden, future Army concepts envision increased mechanication and greater emphasis on mobility and dispersicn. Faced with these problems, the Army searched for other materials arid devices for vehicle propulsion. Nuclear energy seemed to be the apparent answer. H
Solid State Communications, 1976
We have measured the propagation velocities of bulk acoustic waves in the simple cubic transition... more We have measured the propagation velocities of bulk acoustic waves in the simple cubic transition-metal oxide Re03 by ultrasonic pulse propagation. The elastic stiffness constants at 300 K are: C11 = (47.9 ±1.4) x 1011 dyne! cm 2 C~= (6.1 ±0.2) x 1011 dyne/cm2 C 12 = (-0.7 ±2.8) x 1011 dyne/ cm
Proceedings of SPIE - The International Society for Optical Engineering
Proceedings of SPIE - The International Society for Optical Engineering
The 15th Annual Meeting of the IEEE Lasers and Electro-Optics Society
Planar photonic crystals (PPC) are a recent innovation that can permit the miniaturization of opt... more Planar photonic crystals (PPC) are a recent innovation that can permit the miniaturization of optical devices to a scale comparable to the wavelength of light, and their internation in large numbers in the same way as electronic bmponents have been integrated to formmicrochips. The;< Equency bands within which the propagation of electromagnet
Solid State Communications, 1975
ABSTRACT The specific heat and magnetic susceptibility of the transition metal oxide ReO3 have be... more ABSTRACT The specific heat and magnetic susceptibility of the transition metal oxide ReO3 have been measured. The specific heat results give a Debye temperature ΘD = 460 ± 10 K and an electronic specific heat coefficient γ = 6.45 ± 0.07 cal/mole K2 which are in good agreement with similar measurements on the cubic sodium tungsten bronzes. The magnetic susceptibility and the electronic contribution to the specific heat are within a few percent of the corresponding parameters calculated from the free electron model with one electron per unit cell. Our results show that ReO3 behaves much like a simple metal. No experimental evidence for narrow d-band effects was observed.
Physical Review B, 1993
ABSTRACT Yin et al. have reported the use of piezoreflectance to characterize Ge-Si superlattices... more ABSTRACT Yin et al. have reported the use of piezoreflectance to characterize Ge-Si superlattices. Their results show only signals that can be attributed to extended and confined states in bulk Ge, but the method is apparently insensitive to the optical properties of the Ge-Si superlattice itself. In this paper we examine the method used and experimental interpretation proposed by Yin et al. From the data available, we conclude that the piezoreflectance experiment of Yin et al. may be less sensitive than electroreflectance for these superlattice materials, to the degree that it conveys little useful information on the optical properties of Ge-Si structures.
Journal of Optical Communications, 1981
A performance comparison is made between several photodiodes suitable for optical fiber communica... more A performance comparison is made between several photodiodes suitable for optical fiber communications. Si avalanche photodiodes are shown to be the most sensitive, due principally to their low-noise properties. However, the difference in sensitivity between Si detectors and those which respond to 1.3 μιη light, such as Ge, is smallless than a factor of 4 for most bit rates of interest for optical communications. The total attenuation of the optical signal at 1.3 μπι by the fiber is orders of magnitude less than that of 0.85 μπι where Si can be used, thus obliterating the small performance advantage of Si APDs. It will be argued that the great majority of the goals of optical fiber telecommunication can be met without using avalanche gain in the receiver.
Manufacturing LEDs for Lighting and Displays, 2007
ABSTRACT Marketing studies by EPIC show significant revenue opportunities by 2012 for UHB-LEDs in... more ABSTRACT Marketing studies by EPIC show significant revenue opportunities by 2012 for UHB-LEDs in the automotive, LCD backlighting, and architectural lighting sectors. The goal of this workshop on manufacturing issues is to consider five key issues for UHB-LED manufacturing and to propose solutions that will pave the way to full exploitation of the opportunities.
Thin Solid Films, 1992
We studied visible photoluminescence in etched p− silicon films produced by chemical etching and ... more We studied visible photoluminescence in etched p− silicon films produced by chemical etching and electrochemical etching. Topographical examination did not sh.
Thin Solid Films, 1992
ABSTRACT In an attempt to observe the band offset and atomic structure of the SiGe interface dir... more ABSTRACT In an attempt to observe the band offset and atomic structure of the SiGe interface directly we have imaged cross-sections of Si/Ge multilayer structures with scanning tunneling microscopy (STM). The samples were imaged in a nitrogen ambient and consisted of cleaved cross-sections that had been passivated with hydrogen by etching in a NH4F solution. The multilayers were observed by STM, although not with atomic resolution. The conductivity type of the doped layers was determined as a function of position in the cross-section from current-voltage measurements.
Thin Solid Films, 1990
Two of the important developments in strained-layer epitaxy of Si-Ge structures are the demonstra... more Two of the important developments in strained-layer epitaxy of Si-Ge structures are the demonstration of heterojunction bipolar transistors and the increasing evidence that Si-Ge superlattices with direct band gap behavior can be made. The underlying materials growth technologies-limited-reaction chemical vapor deposition and molecular beam epitaxy of symmetrically strained structures-that have made these advances possible, are discussed with an eye toward future developments.
Progress in Quantum Electronics, 1994
Germanium and silicon elemental semiconductors are indirect bandgap, cubic materials that are use... more Germanium and silicon elemental semiconductors are indirect bandgap, cubic materials that are used in the manufacture of the great majority of semiconductor electronic devices. Epitaxial techniques, largely borrowed and adapted from group III-V compound semiconductor technology, have been applied successfully to produce heterostructures and superlattices from Ge and Si. Theory shows that some of these structures behave like direct bandgap materials, while other structures can be used for optical second harmonic generation. On the other hand, it has bean well understood for many years that neither silicon, nor germanium, nor any germanium-silicon alloy could ever show such behaviour. Recent progress in germanium-silicon heterostructures is reviewed in the context of developing a new materials system for photonic devices based entirely on silicon and germanium and suitable for optical waveguides, modulators, sources, and detectors. CONTENTS Introduction 98 Some Materials Considerations for Solid-State Devices using Ge-Si Alloys and Superlattices 2.1. Introduction 2.2. Growth methods 2.3. Fabrication and performance considerations Potential for Ge-Si Electronic and optical devices 3.1. Introduction 3.2. The quantum well infra-red photodiode (QWIP) 3.3. Selection rules for absorption in QWIP structures 3.4. QWIP detectors in p-type. quantum wells 3.5. Electra-modulation of absorption in Ge-Si quantum wells 3.6. The self-electro-optic effect modulator (SEED) Electronic Bandstructure of GeSi Semiconductors 4.1. Introduction 4.2. Electronic bandstructure of some G&i systems 4.3. Calculation of electronic properties: effective mass and mobility 4.4. Measurement of interband transition energies 4.4.
Journal of Physics D: Applied Physics, 1971
IEEE Transactions on Electron Devices, 1975
wavelength range is related to the Frana-Keldysh shift of the absorption edge by the internal ele... more wavelength range is related to the Frana-Keldysh shift of the absorption edge by the internal electric fields due to ionized impurities in the epitaxial GaAs. The variation of the loss coefficient with total ionized impurity concentration will be presented. Measurements of the change in absorption or loss coefficient with applied external electric field E in the range 104 5 E 5 106 V/cm have been made which permit the design of electroabsorption modulators or EAP detectors to obtain 100-percent modulation or internal quantum efficiency, respectively. Experimental results on integrated waveguide modulators and detectors with system limited rise times 60.9 ns and 100-percent efficiency a t 0.91 pm will be described.
IEEE Electron Device Letters, 1981
ABSTRACT Some important consequences of the uncertainty principle on Monte Carlo simulations of v... more ABSTRACT Some important consequences of the uncertainty principle on Monte Carlo simulations of very high field transport are discussed. It is shown that recent values of the phonon scattering rates reported for GaAs by Shichijo and Hess lead to an unrealistically high collisional broadening (0.3-0.6eV) of the electronic states, thus rendering questionable any attempt to relate transport properties to the band structure, and invalidating the semiclassical Boltzmann transport picture used in the Monte Carlo simulation. These considerations are important in the modeling of very high field transport properties in semiconductor devices.
Electronics Letters, 1983
ABSTRACT Ga0.47In0.53As/InP heterophotodiodes are demonstrated with a bandwidth greater than 2 GH... more ABSTRACT Ga0.47In0.53As/InP heterophotodiodes are demonstrated with a bandwidth greater than 2 GHz, less than 0.5 pF capacitance, and subnanoampere dark current at the operating bias. These photodiodes satisfy criteria for both low noise and high speed in the 1 MHz¿2 GHz bit-rate range for optical fibre telecommunications
Electronics Letters, 1983
Applied Physics Letters, 1983
The first successful preparation of optically pumped and current injection Ga0.47In0.53As/Al0.48 ... more The first successful preparation of optically pumped and current injection Ga0.47In0.53As/Al0.48 In0.42As multiquantum well lasers is reported. These devices, operating at room temperature in the 1.5–1.6-μm range, have been prepared by molecular beam epitaxy with well thicknesses as low as 80–90 Å and barrier thicknesses as low as 30 Å. In the broad area devices with a total active layer thickness of 0.14 μm we have observed threshold current density as low as 2.4 kA/cm2.
Performance with the spark-ignition conversion, exceeded that with diesel pilot fuel. Effect of v... more Performance with the spark-ignition conversion, exceeded that with diesel pilot fuel. Effect of varying the compression ratio was also investigated. Direct injection. of liquid ammonia into a high compression ratio (30: 1) engine was attempted and was unsuccessful. Various other auxiliary aids such as fuel at ditives, ionization and radio frequency dissociation were also investigated. A total of 1128 engine test hours were accumulated on the sparkignition engine of which 1045 were with ammonia fuei; 954 hours (911 with ammonia) were accumul'ated onthe compressi t-ignition engine. FOREWORD Logistics studies of Army operations, in World War II and Korea established, that apprcximately 65 percerft of the tbtal tonnage required for support of combat-operations iconsisted of fuels and lubricants. To compound this already heavy logistical, burden, future Army concepts envision increased mechanication and greater emphasis on mobility and dispersicn. Faced with these problems, the Army searched for other materials arid devices for vehicle propulsion. Nuclear energy seemed to be the apparent answer. H
Solid State Communications, 1976
We have measured the propagation velocities of bulk acoustic waves in the simple cubic transition... more We have measured the propagation velocities of bulk acoustic waves in the simple cubic transition-metal oxide Re03 by ultrasonic pulse propagation. The elastic stiffness constants at 300 K are: C11 = (47.9 ±1.4) x 1011 dyne! cm 2 C~= (6.1 ±0.2) x 1011 dyne/cm2 C 12 = (-0.7 ±2.8) x 1011 dyne/ cm
Proceedings of SPIE - The International Society for Optical Engineering
Proceedings of SPIE - The International Society for Optical Engineering
The 15th Annual Meeting of the IEEE Lasers and Electro-Optics Society
Planar photonic crystals (PPC) are a recent innovation that can permit the miniaturization of opt... more Planar photonic crystals (PPC) are a recent innovation that can permit the miniaturization of optical devices to a scale comparable to the wavelength of light, and their internation in large numbers in the same way as electronic bmponents have been integrated to formmicrochips. The;< Equency bands within which the propagation of electromagnet
Solid State Communications, 1975
ABSTRACT The specific heat and magnetic susceptibility of the transition metal oxide ReO3 have be... more ABSTRACT The specific heat and magnetic susceptibility of the transition metal oxide ReO3 have been measured. The specific heat results give a Debye temperature ΘD = 460 ± 10 K and an electronic specific heat coefficient γ = 6.45 ± 0.07 cal/mole K2 which are in good agreement with similar measurements on the cubic sodium tungsten bronzes. The magnetic susceptibility and the electronic contribution to the specific heat are within a few percent of the corresponding parameters calculated from the free electron model with one electron per unit cell. Our results show that ReO3 behaves much like a simple metal. No experimental evidence for narrow d-band effects was observed.
Physical Review B, 1993
ABSTRACT Yin et al. have reported the use of piezoreflectance to characterize Ge-Si superlattices... more ABSTRACT Yin et al. have reported the use of piezoreflectance to characterize Ge-Si superlattices. Their results show only signals that can be attributed to extended and confined states in bulk Ge, but the method is apparently insensitive to the optical properties of the Ge-Si superlattice itself. In this paper we examine the method used and experimental interpretation proposed by Yin et al. From the data available, we conclude that the piezoreflectance experiment of Yin et al. may be less sensitive than electroreflectance for these superlattice materials, to the degree that it conveys little useful information on the optical properties of Ge-Si structures.
Journal of Optical Communications, 1981
A performance comparison is made between several photodiodes suitable for optical fiber communica... more A performance comparison is made between several photodiodes suitable for optical fiber communications. Si avalanche photodiodes are shown to be the most sensitive, due principally to their low-noise properties. However, the difference in sensitivity between Si detectors and those which respond to 1.3 μιη light, such as Ge, is smallless than a factor of 4 for most bit rates of interest for optical communications. The total attenuation of the optical signal at 1.3 μπι by the fiber is orders of magnitude less than that of 0.85 μπι where Si can be used, thus obliterating the small performance advantage of Si APDs. It will be argued that the great majority of the goals of optical fiber telecommunication can be met without using avalanche gain in the receiver.
Manufacturing LEDs for Lighting and Displays, 2007
ABSTRACT Marketing studies by EPIC show significant revenue opportunities by 2012 for UHB-LEDs in... more ABSTRACT Marketing studies by EPIC show significant revenue opportunities by 2012 for UHB-LEDs in the automotive, LCD backlighting, and architectural lighting sectors. The goal of this workshop on manufacturing issues is to consider five key issues for UHB-LED manufacturing and to propose solutions that will pave the way to full exploitation of the opportunities.
Thin Solid Films, 1992
We studied visible photoluminescence in etched p− silicon films produced by chemical etching and ... more We studied visible photoluminescence in etched p− silicon films produced by chemical etching and electrochemical etching. Topographical examination did not sh.
Thin Solid Films, 1992
ABSTRACT In an attempt to observe the band offset and atomic structure of the SiGe interface dir... more ABSTRACT In an attempt to observe the band offset and atomic structure of the SiGe interface directly we have imaged cross-sections of Si/Ge multilayer structures with scanning tunneling microscopy (STM). The samples were imaged in a nitrogen ambient and consisted of cleaved cross-sections that had been passivated with hydrogen by etching in a NH4F solution. The multilayers were observed by STM, although not with atomic resolution. The conductivity type of the doped layers was determined as a function of position in the cross-section from current-voltage measurements.
Thin Solid Films, 1990
Two of the important developments in strained-layer epitaxy of Si-Ge structures are the demonstra... more Two of the important developments in strained-layer epitaxy of Si-Ge structures are the demonstration of heterojunction bipolar transistors and the increasing evidence that Si-Ge superlattices with direct band gap behavior can be made. The underlying materials growth technologies-limited-reaction chemical vapor deposition and molecular beam epitaxy of symmetrically strained structures-that have made these advances possible, are discussed with an eye toward future developments.
Progress in Quantum Electronics, 1994
Germanium and silicon elemental semiconductors are indirect bandgap, cubic materials that are use... more Germanium and silicon elemental semiconductors are indirect bandgap, cubic materials that are used in the manufacture of the great majority of semiconductor electronic devices. Epitaxial techniques, largely borrowed and adapted from group III-V compound semiconductor technology, have been applied successfully to produce heterostructures and superlattices from Ge and Si. Theory shows that some of these structures behave like direct bandgap materials, while other structures can be used for optical second harmonic generation. On the other hand, it has bean well understood for many years that neither silicon, nor germanium, nor any germanium-silicon alloy could ever show such behaviour. Recent progress in germanium-silicon heterostructures is reviewed in the context of developing a new materials system for photonic devices based entirely on silicon and germanium and suitable for optical waveguides, modulators, sources, and detectors. CONTENTS Introduction 98 Some Materials Considerations for Solid-State Devices using Ge-Si Alloys and Superlattices 2.1. Introduction 2.2. Growth methods 2.3. Fabrication and performance considerations Potential for Ge-Si Electronic and optical devices 3.1. Introduction 3.2. The quantum well infra-red photodiode (QWIP) 3.3. Selection rules for absorption in QWIP structures 3.4. QWIP detectors in p-type. quantum wells 3.5. Electra-modulation of absorption in Ge-Si quantum wells 3.6. The self-electro-optic effect modulator (SEED) Electronic Bandstructure of GeSi Semiconductors 4.1. Introduction 4.2. Electronic bandstructure of some G&i systems 4.3. Calculation of electronic properties: effective mass and mobility 4.4. Measurement of interband transition energies 4.4.
Journal of Physics D: Applied Physics, 1971
IEEE Transactions on Electron Devices, 1975
wavelength range is related to the Frana-Keldysh shift of the absorption edge by the internal ele... more wavelength range is related to the Frana-Keldysh shift of the absorption edge by the internal electric fields due to ionized impurities in the epitaxial GaAs. The variation of the loss coefficient with total ionized impurity concentration will be presented. Measurements of the change in absorption or loss coefficient with applied external electric field E in the range 104 5 E 5 106 V/cm have been made which permit the design of electroabsorption modulators or EAP detectors to obtain 100-percent modulation or internal quantum efficiency, respectively. Experimental results on integrated waveguide modulators and detectors with system limited rise times 60.9 ns and 100-percent efficiency a t 0.91 pm will be described.
IEEE Electron Device Letters, 1981
ABSTRACT Some important consequences of the uncertainty principle on Monte Carlo simulations of v... more ABSTRACT Some important consequences of the uncertainty principle on Monte Carlo simulations of very high field transport are discussed. It is shown that recent values of the phonon scattering rates reported for GaAs by Shichijo and Hess lead to an unrealistically high collisional broadening (0.3-0.6eV) of the electronic states, thus rendering questionable any attempt to relate transport properties to the band structure, and invalidating the semiclassical Boltzmann transport picture used in the Monte Carlo simulation. These considerations are important in the modeling of very high field transport properties in semiconductor devices.
Electronics Letters, 1983
ABSTRACT Ga0.47In0.53As/InP heterophotodiodes are demonstrated with a bandwidth greater than 2 GH... more ABSTRACT Ga0.47In0.53As/InP heterophotodiodes are demonstrated with a bandwidth greater than 2 GHz, less than 0.5 pF capacitance, and subnanoampere dark current at the operating bias. These photodiodes satisfy criteria for both low noise and high speed in the 1 MHz¿2 GHz bit-rate range for optical fibre telecommunications
Electronics Letters, 1983
Applied Physics Letters, 1983
The first successful preparation of optically pumped and current injection Ga0.47In0.53As/Al0.48 ... more The first successful preparation of optically pumped and current injection Ga0.47In0.53As/Al0.48 In0.42As multiquantum well lasers is reported. These devices, operating at room temperature in the 1.5–1.6-μm range, have been prepared by molecular beam epitaxy with well thicknesses as low as 80–90 Å and barrier thicknesses as low as 30 Å. In the broad area devices with a total active layer thickness of 0.14 μm we have observed threshold current density as low as 2.4 kA/cm2.